Method of preparing tetrachloroethylene and chlorosilanes



Patented Aug. 1, 1945' METHOD OF PREPARING TETRAOIILOBOQ ETHYLENE AND CHLOBOSHANES Winton I. Patnode, Schenectady, N. Y., and Bobert W. Schiecaler, State College, Pa acsignors to General Electric Company, a corporation of New York No Drawing. Application March 4, 1042, Serial No. 433,829

8 Claims.

ene and, as a secondary product of the reaction,

hexachlorodlsilane, along with other higher or lower boiling materials including silicon tetrachloride.

The silicon employed in the practice of this invention may be used as such in the presence of,

or intimately associated with, the metallic catalyst, or, itmay be used in the form of an alloy with the catalytic metal or metals. Preferably, solid porous contact masses or alloys com-posed of silicon and'a metallic catalyst are employed. Such masses are described and claimed in the copending application of Winton I. Patnode, Serial No. 412,461, filed September 26, 1941, and assigned to the same assignee as the present invention. Copper is the preferred metallic catalyst used to accelerate or control the reaction between the silicon and the carbon tetrachloride. Other catalytic metals which may be used are nickel, tin, antimony, manganese, silver, and titanium.

In order to initiate the desired reaction between the silicon and the carbon tetrachloride, thetemperature should be at least 80 C. but should not be so high as to cause excessive deposition of carbon on the unreacted silicon during the reaction. -The best yields of reaction products boiling above '100" C. are obtained when the reaction temperature is maintained at about.

200-210 C. Higher reaction temperatures, up to 300 C., can be employed but increased carboniza tion at the more elevated temperatures may necessitate frequent renewal of the silicon re actan't.

Preferably the reactionbetween the carbon tetrachloride and silicon is carried out in the presence 01' an inert, gaseous diluent'sueh as nitrogen. The inert gas may be mixed with the carbon tetrachloride vapors as they enter thereaction vessel or the inert gas may epassed through 'a carbon tetrachloride reservoir and thus serve as a carrier for the reactant vapors. Larger yields 01' the desired products and better control of the reaction is possible when the inert gas comprises at least 50 per cent of the gaseous mixture entering the reaction vessel. Other advantages resulting i'rom the general use of such inert gases in carrying out vapor phase reactions between halogenated hydrocarbons and silicon are more. fully set forth in the copending application of M. M. Sprung and W. F. Gilliam, Serial No. 433,293, filed concurrently, herewith and assigned to the same assignee as the present invention.

. In order that those skilled in the art better may understand how the present invention may be carried into eifect the following example is given to illustrate our preferred method of'effecting the reaction between the silicon and carbon tetrachloride:

Example-Dry, oxygen-free nitrogen gas was bubbled through a reservoir of carbon tetrachloride at the rate of about 300 c. 0. per minute and was then passed into a reaction tubev packed with pellets of a silicon-copper alloy containing 90 per cent silicon and 10 per cent copper. These con- .tact masses and their preparation are described and claimed in the Patnode application Serial No, 412,461 referred to hereinbei'ore. By maintaining the temperature of the carbon tetrachloride at approximately -27" C., the carbon tetraabout per cent by weight of a liquid boiling at about 117-118 C. which was identified by its boiling point and its dibromo-derivative, sym.- tetrachlorodibromoethane, as being tetrachloroethylene, ChC=CC12. The next higher-boiling fraction having a boiling range between and 142 C. was a chlorinated silicon compound identified as hexachlorosilane, ClzSi-SiCh'. The composition of residue remaining after the separation of these compounds was not positively determined. Fractionation thereof ata 52 mm. pressure resulted in the clogging of the condenser by a white, crystalline solid which reacted with water to give 01! hydrogen chloride."

The rate at which the carbon tetrachloride may be passed into the reaction tube or vessel depends on the size and temperature of the tube and the rate of dissipation of the heat of reaction. The rate of flow should be determined by trial in each case. When the carbon'tetrachloride vapor is carried into the tube by the nitrogen bubbled through a reservoir of liquid carbon tetrachloride. the rate of introduction thereof can be controlled by the reservoir temperature and/or the rate of iiow of nitrol'en while the relative proportions of the inert gas and the reactant gasinthe mixtureenteringthetubemaybe controlled by varying the reservoir temperature.

Whatweclaimasnewanddesiretosecureby Letters Patent 01 the United States is:

1. The method which comprises eilecting reaction between heated. silicon and carbon tetrachloride in the presence of a metallic catalyst for the reaction.

2. The method which comprises eilecting reaction between carbon tetrachloride in vapor form and heated silicon in the presence 0! an inert gas and a metallic catalyst for the reaction.

3. The method which comprises electing reaction between carbon tetrachloride and the silicon component of a heated, solid,- porous mass of powdered silicon and a metallic catalyst in the presence 0! nitrogen 4. 'rhemethodwhichcompriseseirectingreaction between carbon tetrachloride and silicon at a temperature between 80' and 300' C. in the ot a copper catalyst for the reaction.

5. The method which comprises eilecting reaction between carbon tetrachloride component of a gaseous mixture of nitrocen and carbon tetrachloride and the silicon component 0! a solid. porous mixture of silicon and copper maintained at a temperature of from 80-300 C.

6. The method of preparing tetrachloroethylene from carbon tetrachloride which comprises bringing the carbon tetrachloride in the vapor phase into contact with a mixture 0! silicon and copper at a temperature between 80 and 300 C.

'I. The method of preparing tetrachloroethylene which comprises eflectina reaction between carbon tetrachloride component of a gaseous mixture of nitrogen and carbon tetrachloride and the silicon component of a solid, porous mass of silicon and copper at a temperature between 80' and 300' C. and recovering the tetrachloroethylene from the reaction products.

8. The method which comprises eilecting reaction between the carbon tetrachloride component of a mixture or carbon tetrachloride and nitrogen and the silicon component of a mixture of silicon and copper at a temperature oi about 200-2i0 C. 

